Methods and compositions for reducing the production of water and stimulating hydrocarbon production from a subterranean formation

ABSTRACT

The present invention relates to subterranean treatment fluids, and more particularly, the present invention relates to subterranean treatment fluids comprising relative permeability modifiers and methods for using such subterranean treatment fluids in subterranean operations to reduce the production of water from and stimulate hydrocarbon production in a subterranean formation. In certain embodiments, the methods of the present invention generally comprise the steps of providing a permeability-modifying aqueous treatment fluid comprising a relative permeability modifier and contacting a subterranean formation with the permeability-modifying aqueous treatment fluid. Optionally, the permeability-modifying aqueous treatment fluid may be injected in the subterranean formation at a pressure sufficient to create or enhance at least one fracture therein. In another embodiment, the relative permeability modifier may be provided by appropriate reaction in situ.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 10/760,443 entitled “Methods and Compositions for Reducing theProduction of Water and Stimulating Hydrocarbon Production from aSubterranean Formation,” filed on Jan. 20, 2004, the entire disclosureof which is incorporate herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to subterranean treatment fluids, and moreparticularly, the present invention relates to subterranean treatmentfluids comprising relative permeability modifiers and methods for usingsuch subterranean treatment fluids in subterranean operations to reducethe production of water from and stimulate hydrocarbon production in asubterranean formation.

The production of water with hydrocarbons from subterranean wellsconstitutes a major problem and expense in the production of thehydrocarbons. While hydrocarbon-producing wells are usually completed inhydrocarbon-bearing formations, such formations may contain, or may beadjacent to, water-bearing sections. Generally, the term “water-bearingsection” refers to any portion of a subterranean formation that mayproduce water, including a hydrocarbon-bearing section that hassufficiently high water saturation such that water may be produced alongwith hydrocarbons. The high mobility of the water may allow it to flowinto the well bore by way of natural fractures and/or high permeabilitystreaks present in the formation. Over the life of such wells, the ratioof water to hydrocarbons recovered may be undesirable in view of thecost of producing the water, separating it from the hydrocarbons, anddisposing of it, which can represent a significant economic loss.

Subterranean stimulation treatments have long been used in the field ofhydrocarbon production to increase the flow of hydrocarbons to the wellbore. One such stimulation treatment is hydraulic fracturing, wherespecialized fluids are pumped into the subterranean formation atsufficient pressures to create or enhance at least one fracture withinthe formation, thereby increasing fluid flow through the formation tothe well bore. When a formation contains water-bearing sections,however, stimulation may lead to the undesired, increased production ofwater with the hydrocarbons.

Another subterranean stimulation treatment is acid stimulation (e.g.,“acidizing”), in which an aqueous treatment fluid comprising an acid isintroduced into the formation to dissolve acid-soluble materials thatmay clog or constrict formation channels, thereby potentially wideningthe pathways through which hydrocarbons may flow from the formation intothe well bore. Acid stimulation treatments also may facilitate the flowof injected treatment fluids from the well bore into the formation. Onemethod of acidizing, known as “fracture acidizing,” usually comprisesinjecting an acidizing treatment fluid into the subterranean formationat a pressure sufficient to create or enhance at least one fracturewithin the formation. Another method of acidizing, known as “matrixacidizing,” usually comprises injecting the acidizing treatment fluidinto the formation at a pressure below that which would create orenhance at least one fracture within the subterranean formation. Incertain circumstances, however, the acidizing treatment fluids mayundesirably enter the water-bearing sections instead of thehydrocarbon-bearing sections in the formation because the water-bearingsections may be more permeable to the aqueous acidizing treatment fluidthan the hydrocarbon-bearing sections. Thus, acid stimulation treatmentsmay result in an undesirable increase in the production of water.

A variety of techniques have been used to reduce the production ofundesired water and/or to divert the aqueous acidizing treatment fluidaway from the water-bearing sections and into the hydrocarbon-bearingsections. One attempt has involved the injection of particulates, foams,or blocking polymers into the subterranean formation so as to plug offthe water-bearing sections. Thus, the undesired production of water maybe reduced, and, when used in an acid stimulation treatment, theacidizing treatment fluid may be diverted to the hydrocarbon-bearingsections rather than the water-bearing sections.

However, the use of these water-blocking techniques has proved to beproblematic. For example, plugging off the water-bearing sections maynot be suitable for treating a producing formation unless the injectedsolution (or material) can be injected solely into the offendingwater-bearing sections therein. Further, if a polymer solution isallowed to form a cross-linked polymer gel within ahydrocarbon-producing zone, the gel may reduce or stop the flow ofhydrocarbons in addition to the flow of water. Even when a polymersolution is properly injected into a water-producing section, thecross-linked polymer gel formed therein may become unstable in the zone,due to factors such as thermal degradation, differences in theadsorption characteristics of the polymer and associated cross-linker,and the like. Furthermore, techniques geared toward injecting solutions(or materials) designed to plug off the water-bearing sections arelimited because they may require expensive zonal isolation. Zonalisolation also may be inaccurate, which may lead to inadvertentlyplugging and/or damaging the hydrocarbon-bearing sections.

Recently, polymers referred to as relative permeability modifiers havebeen used, in some instances, to decrease the production of water withhydrocarbons. For example, relative permeability modifiers, such aspolyacrylamide, have been introduced into hydrocarbon andwater-producing formations so that the polymers may attach to adsorptionsites on surfaces within the formations. Among other things, theserelative permeability modifiers may reduce the flow of water through theformation. The use of relative permeability modifiers in hydrocarbon andwater-producing formations to decrease the production of water involvesless risk than other techniques and has the advantage of not requiringexpensive zonal isolation techniques. However, the use of such relativepermeability modifiers, e.g., polyacrylamides, has heretofore resultedin only small, temporary reductions in water production and/orunacceptable levels of reduction in hydrocarbon production.

SUMMARY OF THE INVENTION

The present invention relates to subterranean treatment fluids, and moreparticularly, the present invention relates to subterranean treatmentfluids comprising relative permeability modifiers and methods for usingsuch subterranean treatment fluids in subterranean operations to reducethe production of water from and stimulate hydrocarbon production in asubterranean formation.

One exemplary method of the present invention is a method for treating asubterranean formation to reduce its permeability to aqueous-basedfluids comprising the steps of providing a permeability-modifyingaqueous treatment fluid comprising a hydrophobically modifiedwater-soluble polymer that comprises a polymer backbone comprising polarheteroatoms, and contacting the subterranean formation with thepermeability-modifying aqueous treatment fluid.

Another exemplary method of the present invention is a method fortreating a subterranean formation to reduce its permeability toaqueous-based fluids comprising the steps of providing apermeability-modifying aqueous treatment fluid comprising a hydrophilicpolymer that comprises a polymer backbone comprising polar heteroatoms,a hydrophobic compound capable of reacting with the hydrophilic polymer,and a surfactant; and contacting the subterranean formation with thepermeability-modifying aqueous treatment fluid.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof the exemplary embodiments, which follows.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention relates to subterranean treatment fluids, and moreparticularly, the present invention relates to subterranean treatmentfluids comprising relative permeability modifiers and methods for usingsuch subterranean treatment fluids in subterranean operations to reducethe production of water from and stimulate hydrocarbon production in asubterranean formation.

The methods and compositions of the present invention providepermeability-modifying aqueous treatment fluids that generally comprisea relative permeability modifier, inter alia, that reduces thepermeability of the subterranean formation to aqueous-based fluidswithout substantially changing the permeability to hydrocarbons. Theseaqueous treatment fluids of the present invention may be used, amongother things, in water inhibition operations, hydraulic fracturingoperations, and acid stimulation treatments. In certain embodiments, therelative permeability modifier may be a hydrophobically modifiedwater-soluble polymer, wherein the hydrophobically modifiedwater-soluble polymer may be a reaction product of a hydrophilic polymerand a hydrophobic compound. As used herein, “hydrophobically modified”refers to the incorporation into the hydrophilic polymer structure ofhydrophobic groups, wherein the alkyl chain length is from about 4 toabout 22 carbons. In another embodiment, the relative permeabilitymodifier may be a hydrophilically modified water-soluble polymer,wherein the hydrophilic polymer may a reaction product of a hydrophilicpolymer and a hydrophilic compound. As used herein, “hydrophilicallymodified” refers to the incorporation into the hydrophilic polymerstructure of hydrophilic groups. The reactions needed to form therelative permeability modifiers of the present invention may occur priorto the addition of the relative permeability modifiers into thepermeability-modifying aqueous treatment fluids of the present invention(e.g., pre-reacted embodiments), or they may occur in situ (e.g., insitu reaction embodiments).

I. Exemplary Water Inhibition Embodiments

In an exemplary embodiment, the permeability-modifying aqueous treatmentfluids of the present invention may be used in water inhibitionoperations. When used in water inhibition operations, thepermeability-modifying aqueous treatment fluids may comprise either thepre-reacted embodiments or the in situ reaction embodiments of therelative permeability modifiers. It is believed that the relativepermeability modifiers, among other things, may attach to surfaceswithin the subterranean formation. The presence of the relativepermeability modifiers in the subterranean formation may reduce thepermeability of the treated zones of the subterranean formation toaqueous-based fluids without substantially changing the permeability tohydrocarbons. The desired volume of the permeability-modifying aqueoustreatment fluids introduced into the subterranean formation is based,inter alia, on several properties of the zone to be treated, such asdepth and volume of the zone, as well as the permeability and otherphysical properties of the material in the zone.

A. Exemplary Pre-reacted Embodiments

In the pre-reacted embodiments of the present invention, thepermeability-modifying aqueous treatment fluids of the present inventionmay comprise an aqueous-based fluid and a relative permeabilitymodifier. Also, such permeability-modifying aqueous treatment fluids maybe gelled by the addition of a gelling agent. Further, additivessuitable for use in subterranean treatment operations may be added tothe permeability-modifying aqueous treatment fluids of the presentinvention as desired.

The aqueous-based fluid used in the permeability-modifying aqueoustreatment fluids of the present invention can be fresh water, salt water(e.g., water containing one or more salts, such as potassium chloride,dissolved therein), brine (e.g., saturated salt water), or seawater.Generally, the aqueous-based fluid may be any aqueous liquid providedthat it does not adversely react with the other components of thetreatment fluid. In an exemplary embodiment, the aqueous-based fluidused in the permeability-modifying aqueous treatment fluids of thepresent invention comprises salt water, inter alia, to help inhibit theswelling/migration of clay particles in the subterranean formationsand/or zones being treated. Examples of suitable salts include, but arenot limited to, chloride, bromide, acetate, and formate salts ofammonium, alkyl ammonium, potassium, sodium, calcium, magnesium, andzinc.

In certain embodiments, the relative permeability modifier present inthe permeability modifying aqueous treatment fluids of the presentinvention may be a hydrophobically modified water-soluble polymer. Thehydrophobically modified water-soluble polymers used in the presentinvention typically have a molecular weight in the range of from about100,000 to about 10,000,000. In an exemplary embodiment, thehydrophobically modified water-soluble polymer may comprise a polymerbackbone comprising polar heteroatoms. Generally, the polar heteroatomspresent within the polymer backbone of the hydrophobically modifiedwater-soluble polymer include, but are not limited to, oxygen, nitrogen,sulfur, or phosphorous.

Suitable hydrophobically modified water-soluble polymers may be areaction product of a hydrophilic polymer and a hydrophobic compoundthat are capable of reacting with each other. In certain exemplaryembodiments, the hydrophilic polymers comprise a polymer backbonecomprising polar heteroatoms, wherein the polar heteroatoms presentwithin the polymer backbone of the hydrophilic polymers include, but arenot limited to, oxygen, nitrogen, sulfur, or phosphorous. Suitablehydrophilic polymers comprising polar heteroatoms within the polymerbackbone include homo-, co-, or terpolymers such as, but not limited to,celluloses, chitosans, polyamides, polyetheramines, polyethyleneimines,polyhydroxyetheramines, polylysines, polysulfones, and starches. In anexemplary embodiment the starch is a cationic starch. A suitablecationic starch may be formed by reacting a starch, such as corn, maize,waxy maize, potato, tapioca, and the like, with the reaction product ofepichlorohydrin and trialkylamine.

The hydrophobic compounds that are capable of reacting with thehydrophilic polymers of the present invention include, but are notlimited to, alkyl halides, sulfonates, sulfates, and organic acidderivatives. Examples of suitable organic acid derivatives include, butare not limited to, octenyl succinic acid; dodecenyl succinic acid; andanhydrides, esters, and amides of octenyl succinic acid or dodecenylsuccinic acid. In certain exemplary embodiments, the hydrophobiccompounds may have an alkyl chain length of from about 4 to about 22carbons. For example, where the hydrophobic compound is an alkyl halide,the reaction between the hydrophobic compound and hydrophilic polymermay result in the quaternization of at least some of the hydrophilicpolymer amino groups with an alkyl halide, wherein the alkyl chainlength is from about 4 to about 22 carbons.

In another embodiment, the relative permeability modifier present in thepermeability modifying aqueous treatment fluids of the present inventionmay be a hydrophilically modified water-soluble polymer. Thehydrophilically modified water-soluble polymers used in the presentinvention typically have a molecular weight in the range of from about100,000 to about 10,000,000. In an exemplary embodiment, thehydrophilically modified water-soluble polymer comprises a polymerbackbone comprising polar heteroatoms. Generally, the polar heteroatomspresent within the polymer backbone of the hydrophilically modifiedwater-soluble polymer include, but are not limited to, oxygen, nitrogen,sulfur, or phosphorous.

In one embodiment, the hydrophilically modified water-soluble polymer isa reaction product of a hydrophilic polymer and a hydrophilic compoundthat are capable of reacting with each other. The hydrophilic polymerssuitable for forming the hydrophilically modified water-soluble polymersused in the present invention should be capable of reacting withhydrophilic compounds. In certain exemplary embodiments, suitablehydrophilic polymers include, homo-, co-, or terpolymers such as, butnot limited to, polyvinylamines, poly(vinylamines/vinyl alcohols), andalkyl acrylate polymers in general. Additional examples of alkylacrylate polymers include, but are not limited to,polydimethylaminoethyl methacrylate, polydimethylaminopropylmethacrylamide, poly(acrylamide/dimethylaminoethyl methacrylate),poly(methacrylic acid/dimethylaminoethyl methacrylate),poly(2-acrylamido-2-methyl propane sulfonic acid/dimethylaminoethylmethacrylate), poly(acrylamide/dimethylaminopropyl methacrylamide),poly(acrylic acid/dimethylaminopropyl methacrylamide), andpoly(methacrylic acid/dimethylaminopropyl methacrylamide). In certainembodiments, the hydrophilic polymer contains reactive amino groups inthe polymer backbone or as pendant groups, which are capable of reactingwith hydrophilic compounds. In an exemplary embodiment, the hydrophilicpolymer comprises dialkyl amino pendant groups. In an exemplaryembodiment, the hydrophilic polymer comprises a dimethyl amino pendantgroup and at least one monomer comprising dimethylaminoethylmethacrylate or dimethylaminopropyl methacrylamide.

In another exemplary embodiment, the hydrophilic polymers comprise apolymer backbone comprising polar heteroatoms, wherein the polarheteroatoms present within the polymer backbone of the hydrophilicpolymers include, but are not limited to, oxygen, nitrogen, sulfur, orphosphorous. Suitable hydrophilic polymers comprising polar heteroatomswithin the polymer backbone include homo-, co-, or terpolymers such as,but not limited to, celluloses, chitosans, polyamides, polyetheramines,polyethyleneimines, polyhydroxyetheramines, polylysines, polysulfones,and starches. In an exemplary embodiment the starch is a cationicstarch. A suitable cationic starch may be formed by reacting a starch,such as corn, maize, waxy maize, potato, tapioca, and the like, with thereaction product of epichlorohydrin and trialkylamine.

The hydrophilic compounds suitable for reaction with the hydrophilicpolymers include polyethers comprising halogen; sulfonates; sulfates;and organic acid derivatives. Examples of suitable organic acidderivatives include, but are not limited to, octenyl succinic acid;dodecenyl succinic acid; and anhydrides, esters, and amides of octenylsuccinic acid or dodecenyl succinic acid. Suitable polyethers include,but are not limited to, polyethylene oxides, polypropylene oxides,polybutylene oxides, and mixtures thereof. In an exemplary embodiment,the polyether comprises an epichlorohydrin terminated polyethylene oxidemethyl ether.

The hydrophilically modified water-soluble polymers formed from thereaction of a hydrophilic polymer with a hydrophilic compound haveestimated molecular weights in the range of from about 100,000 to about10,000,000 and may have weight ratios of the hydrophilic polymers to thepolyethers in the range of from about 1:1 to about 10:1. Suitablehydrophilically modified water-soluble polymer having molecular weightsand weight ratios in the ranges set forth above include, but are notlimited to, the reaction product of polydimethylaminoethyl methacrylatewith epichlorohydrin terminated polyethyleneoxide methyl ether; thereaction product of polydimethylaminopropyl methacrylamide withepichlorohydrin terminated polyethyleneoxide methyl ether; and thereaction product of poly(acrylamide/dimethylaminopropyl methacrylamide)with epichlorohydrin terminated polyethyleneoxide methyl ether. In anexemplary embodiment, the hydrophilically modified water-soluble polymercomprises the reaction product of a polydimethylaminoethyl methacrylatewith epichlorohydrin terminated polyethyleneoxide methyl ether having aweight ratio of polydimethylaminoethyl methacrylate to epichlorohydrinterminated polyethyleneoxide methyl ether of 3:1.

Suitable relative permeability modifiers generally should be present inthe permeability-modifying aqueous treatment fluids of the presentinvention in an amount in the range of from about 0.02% to about 10% byweight of the permeability-modifying aqueous treatment fluid. In anotherexemplary embodiment, the relative permeability modifiers are present inthe permeability-modifying aqueous treatment fluids of the presentinvention in an amount in the range of from about 0.05% to about 1.0% byweight of the permeability-modifying aqueous treatment fluid.

In addition, based on formation conditions, the permeability-modifyingaqueous treatment fluids of the present invention may be gelled by theaddition of a suitable gelling agent, for example, a galactomannangelling agent. Galactomannan gelling agents suitable for use in thepermeability-modifying aqueous treatment fluids of the present inventioncomprise naturally occurring gums and their derivatives, such as guar,locust bean, tara, honey locust, tamarind, karaya, tragacanth,carrageenan, and the like. These gums are generally characterized ascomprising a linear backbone having various amounts of galactose unitsattached thereto. The gums also can be characterized as comprising oneor more functional groups such as cis-hydroxyl, hydroxyl, carboxyl,sulfate, sulfonate, amino, or amide. In an exemplary embodiment, thegelling agents suitable for use in the permeability-modifying aqueoustreatment fluids of the present invention comprise at least one or moreof guar, hydroxyethylguar, hydroxypropylguar, carboxymethylguar,carboxymethylhydroxyethylguar, and carboxymethylhydroxypropylguar.

In certain exemplary embodiments wherein the permeability-modifyingaqueous treatment fluids of the present invention are gelled, one ormore of the above-mentioned galactomannan gelling agents may bedissolved in the permeability-modifying aqueous treatment fluids to forma suitable viscous aqueous gel. Generally, the galactomannan gellingagent or agents may be present in the permeability-modifying aqueoustreatment fluids in a sufficient amount to provide the desired gellingof the permeability-modifying aqueous treatment fluids.

The permeability-modifying aqueous treatment fluids may have a pH suitedto the environment of the subterranean formation. For example, thepermeability-modifying aqueous treatment fluids of the present inventioncomprising the pre-reacted relative permeability modifier generally mayhave a pH in the range of from about 4 to about 8.

As known to those skilled in the art, the permeability-modifying aqueoustreatment fluids of the present invention also may contain additionaladditives suitable for use in subterranean operations including, but notlimited to, scale inhibitors, clay stabilizers, and corrosioninhibitors.

Moreover, in an exemplary embodiment, after the permeability-modifyingaqueous treatment fluids of the present invention are injected into thesubterranean formation, an after-flush of a hydrocarbon liquid, such askerosene, diesel oil or crude oil, or a hydrocarbon or inert gas, suchas methane and natural gas or nitrogen (when the formation producesgas), may optionally be introduced into the formation. While notrequired for the modified water-soluble polymer to be effective, theafter-flush may facilitate the subsequent flow of hydrocarbons throughthe formation.

In an exemplary embodiment, prior to injection of the aqueous treatmentfluids of the present invention into the subterranean formation, anoptional pre-flush of a well treatment fluid may be injected into thesubterranean formation. Among other things, the pre-flush cleans theformation to be treated in order to obtain more effective interaction ofthe modified water-soluble polymers with the formation surface. Withoutbeing limited by theory, it is believed that the interaction of therelative permeability modifier with the formation surface may bedependent upon the presence of any existing adsorbed species, forexample, surface impurities, paraffin, asphaltenes, and the like. Thus,a pretreatment step may be necessary for a given formation to betreated.

In an exemplary embodiment, the well treatment fluids used in thepre-flush may comprise a mutual solvent. The mutual solvents suitablefor use in the pre-flush, among other things, may act to removehydrocarbons adhering to formation material. In this regard, any mutualsolvent suitable for solubilizing hydrocarbons may be used in thepre-flush, for example, terpenes (such as limonene), C₃ to C₉ alcohols,glycol-ether (such as ethylene glycol monobutyl ether, “EGMBE”), ormixtures thereof. In another exemplary embodiment, the well treatmentfluids of the pre-flush may further comprise a surfactant. In additionalexemplary embodiments, the well treatment fluids of the pre-flush shouldbe an aqueous fluid that comprises a chemical that interacts with theformation surface within the porous medium and facilitates thepenetration of the modified water-soluble polymer further into thehydrocarbon-bearing section as described in U.S. Pat. No. 6,364,016, therelevant disclosure of which is incorporated herein by reference.

B. Exemplary In situ Reaction Embodiments

In certain embodiments, the relative permeability modifier may be formedby reaction in situ. In an exemplary embodiment, the hydrophobicallymodified water-soluble polymer may be formed by the in situ reactionbetween a hydrophilic polymer and a hydrophobic compound. In theseembodiments, the permeability-modifying aqueous treatment fluids of thepresent invention may comprise an aqueous-based fluid, a hydrophilicpolymer that comprises a polymer backbone comprising polar heteroatoms,a hydrophobic compound capable of reacting with the hydrophilic polymer,and a surfactant. Optionally, the permeability-modifying aqueoustreatment fluids further may comprise a pH-adjusting agent. Also, thepermeability-modifying aqueous treatment fluids may be gelled by theaddition of a gelling agent of the type and amount described above.Further, additives suitable for use in subterranean treatment operationsmay be added to the permeability-modifying aqueous treatment fluids ofthe present invention as desired.

The aqueous-based fluids, hydrophilic polymers, and hydrophobiccompounds for use in these permeability modifying aqueous treatmentfluids may be the same as those described above. Further, thehydrophobically modified polymer formed by the in situ reaction may bethe same as those described above.

The hydrophilic polymer generally should be present in thepermeability-modifying aqueous treatment fluids in an amount necessaryto provide the desired degree of water control. In an exemplaryembodiment, the hydrophilic polymer is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.1% to about 10% by weight ofthe permeability-modifying aqueous treatment fluid. In an exemplaryembodiment, the hydrophilic polymer is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.2% to about 1.5% by weight ofthe permeability-modifying aqueous treatment fluid.

The hydrophobic compound generally should be present in thepermeability-modifying aqueous treatment fluids in an amount necessaryto provide the desired degree of water control. In an exemplaryembodiment, the hydrophobic compound is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.01% to about 5% by weight ofthe permeability-modifying aqueous treatment fluid. In an exemplaryembodiment, the hydrophobic compound is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.02% to about 0.5% by weight ofthe permeability-modifying aqueous treatment fluid.

Further, the in situ reaction between the hydrophilic polymer and thehydrophobic compound generally is effected at subterranean formationtemperatures greater than about 75° F. In an exemplary embodiment, thein situ reaction between the hydrophilic polymer and the hydrophobiccompound is effected at subterranean formation temperatures greater thanabout 100° F.

Depending on certain well bore and formation conditions, a shut-inperiod of from about one minute to several hours may be required topermit the in situ reaction of the hydrophilic polymer and thehydrophobic compound. During the shut-in period, the hydrophilic polymerand the hydrophobic polymer react to form the hydrophobically modifiedwater-soluble polymer. Generally, the length of the well bore and thedownhole temperature should determine the length of any shut-in period.For example, a deep well bore with temperatures greater than or equal toabout 200° F. may not require a shut-in period. Moreover, shallower,cooler formations may require longer shut-in periods that may extend upto about 24 hours. Those skilled in the art will be able to readilydetermine the necessity for, and duration of, any shut-in periods thatmay be useful to permit the appropriate in situ reaction.

Due to the insolubility of hydrophobic compounds in aqueous fluids, asurfactant is present in the permeability-modifying aqueous treatmentfluids of the present invention. The surfactant may be selected based onat least its ability to promote the dissolution of the hydrophobiccompounds in the permeability-modifying aqueous treatment fluids of thepresent invention. The surfactant may be anionic, cationic, amphoteric,or neutral. Surfactants suitable for use in the current inventioninclude, but are not limited to, alkyl ammonium surfactants, betaines,alkyl ether sulfates, alkyl ether sulfonates, and ethoxylated alcohols.Generally, the surfactant is present in the permeability-modifyingaqueous treatment fluids of the present invention in an amount so thatthe hydrophobic compound disperses in the permeability-modifying aqueoustreatment fluids of the present invention. In an exemplary embodiment,the surfactant is present in the treatment fluids of the presentinvention in an amount in the range of from about 0.1% to about 2% byweight of the permeability-modifying aqueous treatment fluid.

Optionally, the permeability-modifying aqueous treatment fluids of thepresent invention may comprise a pH-adjusting agent if desired. ThepH-adjusting agent may facilitate the in situ reaction between thehydrophilic polymer and the hydrophobic compound by providing a suitablepH, e.g., of about 8 or higher, in the permeability-modifying aqueoustreatment fluids of the present invention. Examples of suitablepH-adjusting agents include buffers, alkali metal hydroxides, alkalimetal carbonates, alkali metal phosphates, and other similar compoundsknown by those skilled in the art.

As discussed in the pre-reacted embodiments, an optional pre-flush or anoptional post-flush may be used.

As known to those skilled in the art, the permeability-modifying aqueoustreatment fluids of the present invention also may contain additionaladditives suitable for use in subterranean operations including, but notlimited to, scale inhibitors, clay stabilizers, and corrosioninhibitors.

In another embodiment of the present invention, the hydrophilicallymodified water-soluble polymer may be formed by the in situ reactionbetween a hydrophilic polymer and a hydrophilic compound. In theseembodiments, the permeability modifying treatment fluids of the presentinvention generally comprise an aqueous-based fluid, a hydrophilicpolymer, and a hydrophilic compound. Optionally, thepermeability-modifying aqueous treatment fluids further may comprise apH-adjusting agent. Also, the permeability-modifying aqueous treatmentfluids may be gelled by the addition of a gelling agent of the type andamount described above. Further, additives suitable for use insubterranean treatment operations may be added to thepermeability-modifying aqueous treatment fluids of the present inventionas desired.

The aqueous-based fluids, hydrophilic polymers, hydrophilic compounds,pH-adjusting agent, and gelling agents for use in these permeabilitymodifying aqueous treatment fluids may be the same as those describedabove. Further, the hydrophilically modified polymer formed by the insitu reaction may be the same as those described above.

The hydrophilic polymer generally should be present in thepermeability-modifying aqueous treatment fluids in an amount necessaryto provide the desired degree of water control. In an exemplaryembodiment, the hydrophilic polymer is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.1% to about 10% by weight ofthe permeability-modifying aqueous treatment fluid. In an exemplaryembodiment, the hydrophilic polymer is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.2% to about 1.5% by weight ofthe permeability-modifying aqueous treatment fluid.

The hydrophilic compound generally should be present in thepermeability-modifying aqueous treatment fluids in an amount necessaryto provide the desired degree of water control. In an exemplaryembodiment, the hydrophilic compound is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.01% to about 5% by weight ofthe permeability-modifying aqueous treatment fluid. In an exemplaryembodiment, the hydrophilic compound is present in thepermeability-modifying aqueous treatment fluids of the present inventionin an amount in the range of from about 0.02% to about 0.5% by weight ofthe permeability-modifying aqueous treatment fluid.

Further, the in situ reaction between the hydrophilic polymer and thehydrophilic compound generally is effected at subterranean formationtemperatures greater than about 75° F. In an exemplary embodiment, thein situ reaction between the hydrophilic polymer and the hydrophiliccompound is effected at subterranean formation temperatures greater thanabout 100° F.

Depending on certain well bore and formation conditions, a shut-inperiod of up to about several hours may be required to permit the insitu reaction between the hydrophilic polymer and the hydrophiliccompound. During the shut-in period, the hydrophilic polymer and thehydrophilic compound react to form the hydrophilically modifiedwater-soluble polymer. Generally, the length of the well bore and thedownhole temperature should determine the length of any shut-in period.For example, a deep well bore with temperatures greater than or equal toabout 200° F. may not require a shut-in period. Moreover, shallower,cooler formations should require longer shut-in periods that may extendup to about 24 hours. Those skilled in the art will be able to readilydetermine the necessity for, and duration of, any shut-in periods thatmay be useful to permit the appropriate in situ reaction.

As discussed in the pre-reacted embodiments, an optional pre-flush or anoptional post-flush may be used.

As known to those skilled in the art, the permeability-modifying aqueoustreatment fluids of the present invention also may contain additionaladditives suitable for use in subterranean operations including, but notlimited to, scale inhibitors, clay stabilizers, and corrosioninhibitors.

II. Exemplary Fracture Stimulation Embodiments

In another embodiment, the permeability-modifying aqueous treatmentfluids of the present invention, described above, may be used in thestimulation and/or restimulation of a subterranean formation, e.g.,hydraulic fracturing. In the fracture stimulation embodiments, thepermeability-modifying aqueous treatment fluids of the present inventionmay be used prior to the use of stimulation fluids, simultaneously withthe use of stimulation fluids, and/or independently of stimulationfluids. In an exemplary embodiment, the permeability-modifying aqueoustreatment fluids of the present invention may be injected into asubterranean formation, at a pressure sufficient to create or enhance atleast one fracture therein. Generally, the desired volume of thepermeability-modifying aqueous treatment fluids introduced into thesubterranean formation is based, inter alia, on several properties ofthe zone to be treated, such as depth and volume of the zone, as well asthe permeability and other physical properties of the material in thezone. Where used simultaneously with the use of a stimulation fluid, thepermeability-modifying aqueous treatment fluid and the stimulation fluidmay, in one exemplary embodiment, be injected into the formation atabout the same rate. Furthermore, where used simultaneously with the useof a stimulation fluid, the permeability-modifying aqueous treatmentfluid and the stimulation fluid may be combined prior to their injectioninto the formation.

When used in hydraulic fracturing embodiments, thepermeability-modifying aqueous treatment fluids of the present inventionmay comprise either the pre-reacted embodiments or the in situ reactionembodiments of such permeability-modifying aqueous treatment fluids.Moreover, it is believed that the relative permeability modifierspresent in the aqueous treatment fluids of the present invention (orformed by reaction in situ), may attach to surfaces within thesubterranean formation. The presence of the relative permeabilitymodifiers in the subterranean formation may reduce the permeability ofthe treated zones of the formation to aqueous-based fluids withoutsubstantially changing the permeability to hydrocarbons. As describedabove, where the reaction takes place in situ, a shut-in period of up toabout 24 hours may be beneficial based, inter alia, on factors such asthe downhole temperature and measured depth of the well bore. In anexemplary embodiment, the shut-in period may take place after thestimulation operations are complete.

In an exemplary embodiment, where used in hydraulic fracturing, theaqueous treatment fluids of the present invention further may compriseproppant. Any proppant known to those skilled in the art is suitableincluding, for example, graded sand, bauxite, ceramic materials, glassmaterials, walnut hulls, polymer beads, and the like.

Where injected after the permeability-modifying aqueous treatment fluidsof the present invention, the stimulation fluid, inter alia, shoulddisplace or drive the permeability-modifying aqueous treatment fluidsinto at least one created or enhanced fracture. In an exemplaryembodiment, the stimulation fluid is injected into the subterraneanformation at a pressure sufficient to create or enhance at least onefracture therein. After injection, the gelled (and possibly crosslinked)stimulation fluid may be caused to break, e.g., revert to a less viscousfluid. In an exemplary embodiment, the time needed to break the gel maybe less than or equal to the shut-in period (if any). Afterwards,production of the hydrocarbons may be initiated from the treatedsubterranean formation.

Generally, the stimulation fluid may be any aqueous-based fluid suitablefor use in fracturing operations. In an exemplary embodiment, thestimulation fluid may be gelled. In an exemplary embodiment, thestimulation fluid may be crosslinked. In an exemplary embodiment, thestimulation fluid may comprise proppant. As will be understood by thoseskilled in the art, a variety of conventional additives can be includedin the stimulation fluids of this invention, such as gel stabilizers,gel breakers, clay stabilizers, bactericides, fluid loss additives, andthe like, which do not adversely react with the stimulation fluids orprevent their use in a desired manner.

The following is a nonlimiting list of known methods of fracturing ahydrocarbon-bearing formation that are suitable for use in the presentinvention: U.S. Pat. Nos. 5,944,106 and 6,070,664, the relevantdisclosures of which are incorporated herein by reference. Thesemethods, as well as other methods of fracturing a formation, may bemodified to incorporate the separate step of introducing thepermeability-modifying aqueous treatment fluids of the presentinvention.

III. Exemplary Acid Stimulation Embodiments

As previously mentioned, the permeability-modifying aqueous treatmentfluids of the present invention may be used in acid stimulationtreatments, such as matrix-acidizing and fracture-acidizing processes.In the acid stimulation embodiments, the permeability-modifying aqueoustreatment fluids of the present invention may be used prior to the useof acidizing treatment fluids and/or simultaneously with the use ofacidizing treatment fluids. Where used simultaneously with the use of anacidizing treatment fluid, the permeability-modifying aqueous treatmentfluid and the acidizing treatment fluid may, in one exemplaryembodiment, be injected into the formation at about the same rate.

In the acid stimulation embodiments, the pressure used to inject thepermeability-modifying aqueous treatment fluids of the present inventionmay, but need not, be high enough to create or enhance at least onefracture in the subterranean formation, depending on whether afracture-acidizing or a matrix-acidizing operation is employed. Inmatrix acidizing, the permeability-modifying aqueous treatment fluidsare typically injected into the subterranean formation at a rate belowthe rate that would create a pressure necessary to create or enhance atleast one fracture therein. When used in conjunction with afracture-acidizing operation, the permeability-modifying aqueoustreatment fluids may be injected into the subterranean formation(whether deployed prior to the acidizing treatment fluid, simultaneouslywith the acidizing treatment fluid, or both) at a pressure sufficient tocreate or enhance at least one fracture in the formation. Further, thedesired volume of the permeability-modifying aqueous treatment fluidsintroduced into the subterranean formation is based, inter alia, on thevolume of the acidizing treatment fluid used and on several propertiesof the zone to be treated, such as depth and volume of the zone, as wellas the permeability and other physical properties of the material in thezone. In an exemplary embodiment, where used in fracture acidizingprocesses, the acidizing treatment fluid may be injected into thesubterranean form at a pressure sufficient to create or enhance at leastone fracture therein.

Among other things, the use of the above-mentioned relative permeabilitymodifiers in acid stimulation treatments may provide enhanced diversionof the acidizing treatment fluids within the subterranean formation. Forexample, in one embodiment, the permeability-modifying aqueous treatmentfluids of the present invention may be injected into the subterraneanformation prior to the injection of an acidizing treatment fluid. Therelative permeability modifiers present in the permeability-modifyingaqueous treatment fluids (or formed by reaction in situ) may reduce thepermeability of the treated zone to aqueous-based fluids, which mayretard the migration of such fluids into the treated zone. Morespecifically, the permeability-modifying aqueous-based fluids shouldflow through the areas of least resistance, e.g., the water-bearingsections. It is believed that, in at least one embodiment, the relativepermeability modifiers may attach to surfaces within the water-bearingsections of the formation. The presence of the relative permeabilitymodifiers in the subterranean formation may reduce the permeability ofthe treated zones of the formation to aqueous-based fluids withoutsubstantially changing the permeability to hydrocarbons. Next, amatrix-acidizing treatment fluid (which is an aqueous-based fluid) isinjected into the formation to stimulate the hydrocarbon-bearingsection. Because the relative permeability modifiers within theformation may reduce the flow of aqueous-based fluids through thewater-bearing section, the matrix-acidizing treatment fluid may be atleast partially diverted to another zone of the formation, e.g., fromthe water-bearing section to the hydrocarbon-bearing section.

As desired by one skilled in the art, mechanical methods to isolate thewater-bearing section may be used in conjunction with thepermeability-modifying aqueous treatment fluids of the presentinvention.

The following are some nonlimiting known methods of acidizing ahydrocarbon-bearing formation for use in the present invention: U.S.Pat. Nos. 2,863,832; 2,910,436; 3,215,199; 3,251,415; 3,297,090;3,307,630; and 3,441,085, the relevant disclosures of which areincorporated herein by reference. These methods, as well as othermethods of acidizing a formation, may be modified to incorporate theseparate step of introducing the permeability-modifying aqueoustreatment fluids of the present invention. Moreover, the treatment stepsinvolving the permeability-modifying aqueous treatment fluids of thepresent invention and the acidizing treatment fluids can be repeated asnecessary, or as desired.

As previously discussed, an optional post-flush may be used in the acidstimulation embodiments to facilitate the production of hydrocarbons.Likewise, an optional pre-flush with a well treatment fluid also may beused in the acid stimulation embodiments, inter alia, to clean theformation to be treated.

An exemplary embodiment of a treatment fluid of the present invention isa permeability-modifying aqueous treatment fluid comprising ahydrophobically modified water-soluble polymer that comprises a polymerbackbone comprising polar heteroatoms.

Another exemplary embodiment of a treatment fluid of the presentinvention is a permeability-modifying aqueous treatment fluid comprisinga hydrophilic polymer that comprises a polymer backbone comprising polarheteroatoms, a hydrophobic compound capable of reacting with thehydrophilic polymer, and a surfactant.

An exemplary method of the present invention is a method for treating asubterranean formation to reduce its permeability to aqueous-basedfluids comprising the steps of providing a permeability-modifyingaqueous treatment fluid comprising a hydrophobically modifiedwater-soluble polymer that comprises a polymer backbone comprising polarheteroatoms; and contacting the subterranean formation with thepermeability-modifying aqueous treatment fluid.

Another exemplary method of the present invention is a method fortreating a subterranean formation to reduce its permeability toaqueous-based fluids comprising the steps of providing apermeability-modifying aqueous treatment fluid comprising a hydrophilicpolymer that comprises a polymer backbone comprising polar heteroatoms,a hydrophobic compound capable of reacting with the hydrophilic polymer,and a surfactant; and contacting the subterranean formation with thepermeability-modifying aqueous treatment fluid.

Another exemplary method of the present invention is a method forfracturing a subterranean formation comprising the steps of providing apermeability-modifying aqueous treatment fluid comprising ahydrophobically modified water-soluble polymer that comprises a polymerbackbone comprising polar heteroatoms; and injecting thepermeability-modifying aqueous treatment fluid into the subterraneanformation at a pressure sufficient to create or enhance at least onefracture therein.

Another exemplary method of the present invention is a method forfracturing a subterranean formation comprising the steps of providing apermeability-modifying aqueous treatment fluid comprising a hydrophilicpolymer that comprises a polymer backbone comprising polar heteroatoms,a hydrophobic compound capable of reacting with the hydrophilic polymer,and a surfactant; and injecting the treatment fluid into thesubterranean formation at a pressure sufficient to create or enhance atleast one fracture therein.

Another exemplary method of the present invention is a method foracidizing a subterranean formation penetrated by a well bore comprisingthe steps of providing a permeability-modifying aqueous treatment fluidcomprising a relative permeability modifier comprising a hydrophobicallymodified water-soluble polymer that comprises polar heteroatoms withinthe polymer backbone or a hydrophilically modified water-solublepolymer; providing an acidizing treatment fluid; injecting thepermeability-modifying aqueous treatment fluid into the subterraneanformation; and injecting the acidizing treatment fluid into thesubterranean formation.

Another exemplary method of the present invention is a method foracidizing a subterranean formation penetrated by a well bore comprisingthe steps of providing a permeability-modifying aqueous treatment fluidcomprising a hydrophilic polymer that comprises a polymer backbonecomprising polar heteroatoms, a hydrophobic compound capable of reactingwith the hydrophilic polymer, and a surfactant; providing an acidizingtreatment fluid; injecting the permeability-modifying aqueous treatmentfluid into the subterranean formation; and injecting the acidizingtreatment fluid into the subterranean formation.

Another exemplary method of the present invention is a method foracidizing a subterranean formation penetrated by a well bore comprisingthe steps of providing a permeability-modifying aqueous treatment fluidcomprising a hydrophilic polymer and a hydrophilic compound capable ofreacting with the hydrophilic polymer; providing an acidizing treatmentfluid; injecting the permeability-modifying aqueous treatment fluid intothe subterranean formation; and injecting the acidizing treatment fluidinto the subterranean formation.

To facilitate a better understanding of the present invention, thefollowing examples of preferred embodiments are given. In no way shouldthe following examples be read to limit, or to define, the scope of theinvention.

EXAMPLE 1

Permeability reduction tests were performed using two treatmentsolutions and a multipressure tap Hassler sleeve containing a Bereasandstone core. These permeability reduction tests were performed at175° F. Further, Test No. 1 was conducted using a brine containing 2% byweight potassium chloride, and Test No. 2 was conducted using a brinecontaining 7% potassium chloride. Two treatment solutions were preparedfor this series of tests.

The treatment solution used in Test No. 1 comprised 5,000 ppm of asample polymer and 500 ppm of “ARQUAD® DMCB 80” dissolved in 2%potassium chloride brine. “ARQUAD® DMCB 80” is a surfactant that iscommercially available from Akzo Nobel Inc., Chicago, Ill. The samplepolymer comprises a hydrophobically modified water-soluble polymer thatcomprises a polymer backbone comprising polar heteroatoms formed fromthe reaction of a cationic starch and an organic acid derivative, suchas octenyl acid or dodecenyl succinic acid.

The treatment solution used in Test No. 2 comprised 5,000 ppm of thesample polymer dissolved in 7% potassium chloride brine.

The following procedure was used for this series of tests, the resultsof which are provided in Table 1. For each test, the above-describedbrines were flowed through the Berea core, followed by oil (kerosene),followed by brine. This third brine flow was maintained until thepressure stabilized, yielding an initial brine permeability. Next, atreatment solution was flowed into the core. Next, the brine flow wasreestablished until the pressure stabilized, yielding a finalpermeability from which the brine permeability was calculated using theformula [1−(final permeability/initial permeability)]×100. Themultipressure tap Hassler sleeve allowed the core permeability to bedivided into four segments. In the tests, the initial brine flow wasfrom segment 1 to segment 4. The treatment solution flow was fromsegment 4 to segment 1, and the final brine flow was from segment 1 tosegment 4. The results of the tests are provided below in Table 1. TABLE1 Sample Polymer Initial Water Water Concentration SurfactantPermeability Permeability Test (ppm) Brine Surfactant Concentration(milli Darcy) Reduction Test 5000 2% ARQUAD 500 ppm 90 85% No. 1 KCLDMCB-80 Test 5000 7% None None 120 69% No. 2 KCL

This example indicates, inter alia, that a relative permeabilitymodifier used in the permeability-modifying aqueous treatment fluids ofthe present invention may reduce the permeability of a formation toaqueous-based fluids.

Therefore, the present invention is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as thosewhich are inherent therein. While numerous changes may be made by thoseskilled in the art, such changes are encompassed within the spirit ofthis invention as defined by the appended claims.

1. A method for treating a subterranean formation penetrated by a wellbore to reduce its permeability to aqueous-based fluids comprising thesteps of: providing a permeability-modifying aqueous treatment fluidcomprising a hydrophobically modified water-soluble polymer thatcomprises a polymer backbone comprising polar heteroatoms; andcontacting the subterranean formation with the permeability-modifyingaqueous treatment fluid.
 2. The method of claim 1 wherein contacting thesubterranean formation with the permeability-modifying aqueous treatmentfluid involves injecting the permeability-modifying aqueous treatmentfluid into the subterranean formation.
 3. The method of claim 1 whereinthe permeability-modifying aqueous treatment fluid further comprises anaqueous-based fluid.
 4. The method of claim 1 wherein thehydrophobically modified water-soluble polymer has a molecular weight inthe range of from about 100,000 to about 10,000,000.
 5. The method ofclaim 1 wherein the polar heteroatoms present within the polymerbackbone of the hydrophobically modified water-soluble polymer areselected from the group consisting of oxygen, nitrogen, sulfur, andphosphorous.
 6. The method of claim 1 wherein the hydrophobicallymodified water-soluble polymer is present in the permeability-modifyingaqueous treatment fluid in an amount in the range of from about 0.02% toabout 10% by weight of the permeability-modifying aqueous treatmentfluid.
 7. The method of claim 1 wherein the hydrophobically modifiedwater-soluble polymer is a reaction product of a hydrophilic polymerthat comprises a polymer backbone comprising polar heteroatoms and ahydrophobic compound.
 8. The method of claim 7 wherein the hydrophilicpolymer is selected from the group consisting of a cellulose, achitosan, a polyamide, a polyetheramine, a polyethyleneimine, apolyhydroxyetheramine, a polylysine, a polysulfone, and a starch.
 9. Themethod of claim 8 wherein the starch comprises a cationic starch. 10.The method of claim 7 wherein the hydrophobic compound is selected fromthe group consisting of an alkyl halide, a sulfonate, a sulfate, and anorganic acid derivative.
 11. The method of claim 10 wherein the organicacid derivative comprises an octenyl succinic acid; a dodecenyl succinicacid; or an anhydride, ester, or amide of octenyl succinic acid ordodecenyl succinic acid.
 12. The method of claim 7 wherein thehydrophobic compound has an alkyl chain length of from about 4 to about22 carbons.
 13. The method of claim 1 wherein the permeability-modifyingaqueous treatment fluid further comprises a gelling agent.
 14. Themethod of claim 1 further comprising the step of injecting a fracturestimulation fluid into the subterranean formation at a pressuresufficient to create or enhance at least one fracture therein afterinjection of the permeability-modifying aqueous treatment fluid into theformation.
 15. The method of claim 1 further comprising the step ofinjecting a fracture stimulation fluid into the subterranean formationat a pressure sufficient to create or enhance at least one fracturetherein before injection of the permeability-modifying aqueous treatmentfluid into the formation.
 16. The method of claim 1 further comprisingthe step of injecting a hydrocarbon liquid or a gas into thesubterranean formation after injection of the permeability-modifyingaqueous treatment fluid.
 17. The method of claim 1 further comprisingthe step of injecting a well treatment fluid comprising a mutual solventinto the subterranean formation prior to injection of thepermeability-modifying aqueous treatment fluid.
 18. A method fortreating a subterranean formation penetrated by a well bore to reduceits permeability to aqueous-based fluids comprising the steps of:providing a permeability-modifying aqueous treatment fluid comprising ahydrophilic polymer that comprises a polymer backbone comprising polarheteroatoms, a hydrophobic compound capable of reacting with thehydrophilic polymer, and a surfactant; and contacting the subterraneanformation with the permeability-modifying aqueous treatment fluid. 19.The method of claim 18 wherein contacting the subterranean formationwith the permeability-modifying aqueous treatment fluid involvesinjecting the permeability-modifying aqueous treatment fluid into thesubterranean formation.
 20. The method of claim 18 wherein thepermeability-modifying aqueous treatment fluid further comprises anaqueous-based fluid.
 21. The method of claim 18 further comprising thestep of the hydrophilic polymer and the hydrophobic compound reacting insitu to form a hydrophobically modified water-soluble polymer thatcomprises a polymer backbone comprising polar heteroatoms.
 22. Themethod of claim 21 wherein the polar heteroatoms present within thepolymer backbone of the hydrophobically modified water-soluble polymerare selected from the group consisting of oxygen, nitrogen, sulfur, orphosphorous.
 23. The method of claim 18 wherein the hydrophilic polymeris selected from the group consisting of a cellulose, a chitosan, apolyamide, a polyetheramine, a polyethyleneimine, apolyhydroxyetheramine, a polylysine, a polysulfone, and a starch. 24.The method of claim 18 wherein the polar heteroatoms present within thepolymer backbone of the hydrophilic polymer comprise oxygen, nitrogen,sulfur, or phosphorous.
 25. The method of claim 18 wherein thehydrophilic polymer is present in the permeability-modifying aqueoustreatment fluid in an amount in the range of from about 0.1% to about10% by weight of the permeability-modifying aqueous treatment fluid. 26.The method of claim 18 wherein the hydrophobic compound is selected fromthe group consisting of an alkyl halide, a sulfonate, a sulfate, and anorganic acid derivative.
 27. The method of claim 18 wherein thehydrophobic compound has an alkyl chain length of from about 4 to about22 carbons.
 28. The method of claim 18 wherein the hydrophobic compoundis present in the permeability-modifying aqueous treatment fluid in anamount in the range of from about 0.01% to about 5% by weight of thepermeability-modifying aqueous treatment fluid.
 29. The method of claim18 wherein the surfactant comprises an anionic, a cationic, anamphoteric, or a neutral surfactant.
 30. The method of claim 18 whereinthe surfactant is present in the permeability-modifying aqueoustreatment fluid in an amount in the range of from about 0.1% to about2.0% by weight of the permeability-modifying aqueous treatment fluid.31. The method of claim 18 wherein the permeability-modifying aqueoustreatment fluid further comprises a gelling agent.
 32. The method ofclaim 18 wherein the permeability-modifying aqueous treatment fluidfurther comprises a pH-adjusting agent that adjusts the pH to at leastabout
 8. 33. The method of claim 32 wherein the pH-adjusting agentcomprises a buffer, an alkali metal hydroxide, an alkali metalcarbonate, or an alkali metal phosphate.
 34. The method of claim 18further comprising the step of shutting the well bore for a period offrom about 1 minute to about 24 hours.
 35. The method of claim 18further comprising the step of injecting a fracture stimulation fluidinto the subterranean formation at a pressure sufficient to create orenhance at least one fracture therein after injection of thepermeability-modifying aqueous treatment fluid into the formation. 36.The method of claim 18 further comprising the step of injecting afracture stimulation fluid into the subterranean formation at a pressuresufficient to create or enhance at least one fracture therein beforeinjection of the permeability-modifying aqueous treatment fluid into theformation.